Observations of oceanic-forced subtidal elevations in a convergent estuary

Remotely-forced downwelling events are found to generate oceanic subtidal elevations along the Pacific Northwest that are transmitted upstream in a large, river-tide, convergent Columbia River estuary (CRE). The oceanic subtidal generation mechanism was evaluated using NOAA tidal and USGS river gage station data along the northern California, Oregon, and Washington estuaries and throughout the Columbia River and the NOAA Coastal Upwelling Index. Oceanic downwelling-induced subtidal motions propagate upstream with a slight decrease in amplitude. River discharge pulses also generate subtidal motions that propagate downstream with decreasing amplitude. The relative oceanic subtidal motions represent 90% of the total subtidal contribution near the entrance that decrease to 40% at 169 km upstream.